JPWO2019187226A1 - Perpendicular magnetic recording medium - Google Patents

Abstract

The vertical magnetic recording medium of the present invention contains a metal oxide as a non-magnetic material, and the magnetic material is formed on the granular layer 2 in which the magnetic material is dispersed in the non-magnetic material and the granular layer 2 and does not contain the metal oxide. A vertical magnetic recording medium having the cap layer 3 as a layer forming at least a part of the recording layer 1, and the oxide phase of the boundary portion of the granular layer directly below the cap layer 3 with the cap layer is It contains at least one selected from the group consisting of Zn, W, Mn, Fe and Mo.

Description

In the present invention, as a layer constituting at least a part of the recording layer, a granular layer in which a magnetic material is dispersed in a non-magnetic material containing a metal oxide, and a cap layer formed on the granular layer and containing no metal oxide. The present invention relates to a vertical magnetic recording medium having the above, and in particular, proposes a technique capable of contributing to the improvement of the inverting magnetic field dispersion (SFD) required for high-density recording.

For hard disk drives, a perpendicular magnetic recording method that records magnetism in the direction perpendicular to the recording surface has been put into practical use, and this method enables high-density recording compared to conventional in-plane magnetic recording methods. Widely adopted.

The perpendicular magnetic recording medium is generally configured by sequentially laminating a soft magnetic layer, an intermediate layer, a recording layer, and the like on a substrate such as aluminum or glass. Among these, the recording layer has a granular layer in which a non-magnetic material of _{SiO 2} or other metal oxide is dispersed in a magnetic material such as a Co-Pt-based alloy containing Co as a main component. As a result, in the recording layer, the above-mentioned metal oxide, which is a non-magnetic material, is deposited on the grain boundaries of magnetic particles of a magnetic material such as a Co alloy oriented in the vertical direction, and the magnetic particles are magnetically arranged. The interaction is reduced, which improves the noise characteristics and achieves a high recording density. As a technique related to this, there is one described in Patent Document 1.

Each layer of such a magnetic recording medium is usually formed by sputtering with a magnetron sputtering apparatus using a sputtering target having a predetermined composition corresponding to the layer, for example, as described in Patent Document 2. Will be done.

Japanese Patent No. 4021435 Japanese Patent No. 5960287

In the recording layer of the perpendicular magnetic recording medium as described above, the recording layer generally has, in addition to the granular layer, a cap layer formed on the granular layer and containing no metal oxide and mainly composed of a magnetic material. According to this, while low noise is realized by the particle separability of the granular layer in which the magnetic particles are magnetically separated by the metal oxide, the interaction between the magnetic particles is left by the absence of the metal oxide. The cap layer imparts an appropriate interaction between magnetic particles to the granular layer, ensuring writeability of the medium, reduction of SFD, thermal stability, and the like.

By the way, when a cap layer is formed on the granular layer by sputtering or the like in order to form a recording layer of such a perpendicular magnetic recording medium, the wettability between the metal oxide in the granular layer and the metal of the cap layer is wet. Due to the difference, the thin film of the cap layer selectively grows in the portion of the granular layer in which the metal oxide does not exist. As a result, the initial growth of the thin film of the cap layer becomes non-uniform following the morphology of the granular layer containing the metal oxide. Therefore, even if the cap layer having a predetermined thickness is formed, the reversing magnetic field dispersion (SFD: switching field) There was a problem that the dispersion) did not improve. On the other hand, if the cap layer is formed thick, the SFD is improved, but the distance between the head and the center of the medium is increased and the resolution is lowered, and the thick cap layer increases the exchange bond between the magnetic particles and increases the magnetic cluster size. It cannot be increased to increase the recording density.

An object of the present invention is to solve such a problem of a conventional perpendicular magnetic recording medium, and an object of the present invention is to uniformly stack a cap layer on a granular layer of a recording layer, thereby improving efficiency. An object of the present invention is to provide a perpendicular magnetic recording medium capable of improving inverting magnetic field dispersion (SFD).

As a result of diligent studies, the inventor made the oxide of the metal and Co, etc. by including the oxide of a predetermined metal in the boundary portion of the granular layer located directly below the cap layer in the recording layer with the cap layer. Based on the good wettability with the cap layer containing a large amount of, the cap layer will be laminated on the non-magnetic part of the granular layer as well as on the magnetic part of the granular layer from the early stage of its growth. As a result, it was found that a uniform cap layer was formed on the granular layer. Further, since the oxide of a predetermined metal effectively separates the magnetic particles, when used as the metal oxide at the boundary portion of the granular layer, the required magnetic separability of the magnetic particles in the granular layer can be realized. it can.

Based on this finding, the vertical magnetic recording medium of the present invention contains a metal oxide as a non-magnetic material, and the magnetic material is formed on a granular layer in which the magnetic material is dispersed in the non-magnetic material and the metal oxide. The oxide phase of the granular layer immediately below the cap layer at the boundary with the cap layer is Zn, W. , Mn, Fe and Mo, which contain at least one selected from the group.

In the vertical magnetic recording medium of the present invention, it is preferable that the oxide phase at the boundary portion of the granular layer contains at least Zn among the above metals.
In the vertical magnetic recording medium of the present invention, the oxide phase at the boundary portion of the granular layer may further contain at least one of B and Si, and the granular layer may contain at least one of the above. The oxide phase at the boundary portion can further contain Ti.

The perpendicular magnetic recording medium of the present invention preferably has a Zn-free layer in the rest of the granular layer except for the boundary portion.
In this case, the remaining portion of the granular layer contains an oxide of at least one element selected from the group consisting of Si, B and Ti as the oxide phase, and the total content of the oxide of the oxide phase in the remaining portion is contained. The amount is 20 vol. % ~ 50 vol. % Is even more preferable.

Further, in the vertical magnetic recording medium of the present invention, it is preferable that the oxide phase at the boundary portion of the granular layer contains Zn and the Zn content of the oxide phase is 3 at% or more.

Further, in the perpendicular magnetic recording medium of the present invention, the ratio of the thickness of the boundary portion to the thickness of the entire granular layer is preferably 3% to 50% in the stacking direction of the recording layers.

Here, it is assumed that the magnetic particles of the entire granular layer including the boundary portion contain at least one metal selected from the group consisting of Co as a main component and Pt, Ru and Cr as the magnetic material. Can be done. This magnetic material can have a so-called ECL (Exchange Coupling Layer) which is vertically divided by a non-magnetic layer mainly composed of Co or Ru.
Further, the cap layer may be mainly composed of Co and further contain at least one metal selected from the group consisting of Cr, Pt and B.

Further, in the perpendicular magnetic recording medium of the present invention, the thickness of the cap layer is preferably 1 nm to 3 nm in the stacking direction of the recording layers.

According to the vertical magnetic recording medium of the present invention, the oxide phase of the granular layer immediately below the cap layer at the boundary with the cap layer contains the above-mentioned metal, so that the granular layer is formed from the initial stage of growth of the cap layer. Since the cap layer also grows on the non-magnetic portion of the oxide phase containing the metal, the cap layer is uniformly laminated on the granular layer, whereby the reversal magnetic field dispersion (SFD) can be improved.

It is sectional drawing which shows typically the recording layer of the perpendicular magnetic recording medium of one Embodiment of this invention, along the stacking direction of the recording layer. It is sectional drawing which shows typically the recording layer of the conventional perpendicular magnetic recording medium along the stacking direction of the recording layer. It is a graph which shows the change of Ra with the increase of the film thickness tc of a cap layer at the time of sputtering of the test example 1 of an Example. It is a graph which shows the change of −Hn with the increase of the film thickness tc of a cap layer at the time of sputtering of Test Example 1 of an Example. It is a graph which shows the relationship between the Zn content in Test Example 3 of an Example, and the film thickness of a cap layer which Ra of Ra of a cap layer becomes less than 5 Å. It is a graph which shows the relationship between the Zn content in Test Example 3 of an Example, and the film thickness of a cap layer in which −Hn becomes positive.

Hereinafter, embodiments of the present invention will be described in detail.
The perpendicular magnetic recording medium of one embodiment of the present invention includes a recording layer, and as illustrated in FIG. 1, the recording layer 1 contains a metal oxide as a non-magnetic material as a layer constituting at least a part thereof. It has a granular layer 2 in which a magnetic material is dispersed in the non-magnetic material, and a cap layer 3 formed on the granular layer 2 and containing no metal oxide. Therefore, in the recording layer 1 of this embodiment, the granular layer 2 contains an oxide phase 4a made of a non-magnetic material and a metal phase 4b made of a magnetic material, while the cap layer 3 does not contain a metal oxide. Consists of only certain metals.

The perpendicular magnetic recording medium may be, for example, a substrate, a soft magnetic layer, an intermediate layer, and the recording layer 1 laminated in this order, and among them, those other than the recording layer 1 are the same as before. Therefore, the description thereof is omitted here. Further, the recording layer 1 of this embodiment is composed of a granular layer 2 and a cap layer 3, but may further include a non-magnetic or magnetic Onset layer having a small magnetic moment, an ECL layer, or the like. There is.

(Cap layer)
The cap layer 3 does not contain a metal oxide and is made of only a magnetic metal. Specifically, such a metal is mainly composed of Co and is further selected from the group consisting of Cr, Pt and B. Can be mentioned as containing at least one kind of metal.
The metal constituting the cap layer 3 is typically composed mainly of Co and Pt, and may optionally contain one or more metals selected from the group consisting of Cr and B. The cap layer 3 is usually an alloy mainly composed of CoCrPtB.

In this embodiment, as will be described later, when the cap layer 3 is formed, the cap layer 3 can be uniformly laminated on the granular layer 2 from the initial stage of the film formation, so that the thickness ct of the cap layer 3 is required. Inverted magnetic field dispersion (SFD) can be efficiently improved without making it thicker than this. The thickness tc of the cap layer 3 is a percentage of the total thickness tg of the granular layer 2, and is preferably 3% to 30%. Specifically, the thickness tc of the cap layer 3 is preferably 0.5 nm to 3 nm.

(Granular layer)
The entire granular layer 2 is composed of an oxide phase 4a made of a non-magnetic metal oxide and a magnetic metal phase 4b. The granular layer 2 is viewed in the stacking direction of the recording layer 1. As shown in FIG. 1, it may be composed of at least two layers including a boundary portion 2a located immediately below the cap layer 3 and a remaining portion 2b located below the boundary portion 2a other than the boundary portion 2a. It is essential. The boundary portion 2a and the remaining portion 2b differ in the metal oxide constituting the oxide phase 4a.

Specifically, the oxide phase 4a of the boundary portion 2a is assumed to contain at least one selected from the group consisting of Zn, W, Mn, Fe and Mo, and preferably contains Zn. Here, the oxide contained in the boundary portion 2a is mainly ZnO.
According to this, when the cap layer 3 is formed on the granular layer 2 by sputtering, the metal constituting the cap layer 3 containing no metal oxide and ZnO at the boundary portion 2a of the granular layer 2 are formed. By exhibiting good wettability, the constituent metals of the cap layer 3 can be uniformly laminated on the entire boundary portion 2a of the granular layer 2 including the oxide phase 4a from the initial stage of growth of the cap layer 3. As a result, the function of the cap layer 3 is effectively exhibited, and the inverting magnetic field dispersion (SFD) can be improved. Further, since ZnO can effectively separate the magnetic particles of the metal phase 4b of the granular layer 2, the required magnetic separability is ensured even at the boundary portion 2a of the granular layer 2 substantially in the same manner as the remaining portion 2b. be able to.

In the conventional vertical magnetic recording medium, as shown in FIG. 2, the oxide phase 14a of the granular layer 12 is made of an oxide of a metal other than the above-mentioned metal in the entire stacking direction. When the layer 13 is formed, the metal of the cap layer 13 is selectively laminated on the metal phase 14b of the granular layer 12 in which the metal oxide does not exist at the initial stage of its growth. That is, as schematically shown in FIG. 2, in the lower part of the cap layer 13 close to the granular layer 12, there is a portion where the metal of the cap layer 13 cannot be laminated due to excellent crystallinity, so-called epitaxial growth. As a result, even if the cap layer 13 having a predetermined thickness is formed, the improvement of the inverting magnetic field dispersion (SFD) cannot be realized. It is also considered that this can be prevented by making the cap layer 13 sufficiently thick, but in this case, the distance between the head and the center of the medium becomes large and the resolution decreases, and the thick cap layer 13 between the magnetic particles. There is another problem that the exchange coupling becomes large and the magnetic cluster size increases and the recording density cannot be increased.
In the embodiment of the present invention as shown in FIG. 1, since the oxide phase of the boundary portion 2a contains Zn, W, Mn, Fe and / or Mo which are easily wetted with the cap layer 3, such a conventional method is used. The problem can be solved effectively.

When the boundary portion 2a of the granular layer 2 contains Zn, the Zn content thereof is preferably 3 at% or more. When the Zn content of the boundary portion 2a is less than 3 at%, improvement in wettability cannot be expected, the cap layer may be difficult to grow epitaxially on the oxide phase, and the Zn content of the boundary portion 2a When is more than 25 at%, there is a concern that the magnetic anisotropy and crystallinity may be lowered due to the large amount of Zn entering the metal phase.

The oxide phase of the boundary portion 2a of the granular layer 2 is at least one selected from the group consisting of Zn, W, Mn, Fe, and Mo to improve wettability, B and Si to improve amorphousness, and separation. It is even more preferable to use a metal oxide containing Ti that improves the properties. That is, the oxide phase of the boundary portion 2a of the granular layer 2 may contain at least one selected from the group consisting of Zn, W, Mn, Fe and Mo, but in addition to that, It can contain at least one of B and Si, and / or Ti.

When viewed in the stacking direction of the recording layer, the ratio (tb / tg) of the thickness tb of the boundary portion 2a of the granular layer 2 to the total thickness tg of the granular layer 2 shall be 3% to 50% as a percentage. Is preferable. If this ratio (tb / tg) of the thickness tb of the boundary portion 2a to the total thickness tg is less than 3%, the effect of uniform film formation of the cap layer 3 by ZnO of the boundary portion 2a may not be sufficiently obtained. is there. The ratio (tb / tg) of the thickness tb of the boundary portion 2a to the total thickness tg of the granular layer 2 is more preferably 3% to 30%.

On the other hand, the oxide phase of the remaining portion 2b of the granular layer 2 which does not significantly affect the uniform film formation of the cap layer 3 may contain Zn as in the boundary portion 2a, but Zn is used. It is preferable that it does not contain it. Further, it is preferable that the remaining portion 2b of the granular layer 2 is a layer containing not only ZnO but also Zn. This is because if the remaining portion 2b of the granular layer 2 contains Zn, there is a concern that the magnetic anisotropy Ku may decrease.

The remaining portion 2b of the granular layer 2 contains, as the oxide phase, an oxide of at least one element selected from the group consisting of Si, B and Ti, instead of a predetermined metal oxide such as ZnO as described above. Can be. The total content of oxides in the balance 2b, including oxides other than the oxides, is preferably 20 vol. % ~ 50 vol. %. The total content of oxides in the balance 2b is 20 vol. If it is less than%, the separation of the metal phase may be insufficient and the magnetic cluster size may increase, and 50 vol. If it exceeds%, the proportion of the metal phase is small and sufficient Ku and magnetic anisotropy cannot be obtained, which may result in insufficient thermal stability and reproduction signal strength. The volume fraction of the oxide in the film is determined by TEM observation.

The metal phase 4b, which is the magnetic material of the granular layer 2, is mainly composed of Co and further contains at least one metal selected from the group consisting of Pt, Ru and Cr.

Next, the perpendicular magnetic recording medium of the present invention was prototyped and its performance was evaluated, which will be described below. However, the description here is for the purpose of mere illustration, and is not intended to be limited thereto.

(Test Example 1)
As Example 1-1, Cr-Ti (6 nm), Ni-W (5 nm), and Ru (20 nm) are deposited on a glass substrate in this order by a magnetron sputtering apparatus (C-3010 sputtering system manufactured by Canon Anerva). _{Co-Pt-SiO 2} (10 nm) was formed as a lower granular layer (the rest of the granular layer) on the resulting layer, and an upper granular layer (granular layer) was formed on the coating using a sputtering target composed of Co-Pt-ZnO. (Boundary portion with the cap layer) is sputtered at 300 W in an Ar5.0Pa atmosphere to form each magnetic film having a film thickness of 3 nm, and Co-Cr-Pt-B (Co-Cr-Pt-B) as a cap layer is formed on the magnetic film. (0 to 8 nm) was formed to form each layer. In Example 1-1, the oxide of the upper granular layer is made of ZnO.

Further, as Examples 1-2 to Example 1-5, a film similar to that of Example 1 was formed except that the oxide of the upper granular layer was composed of WO ₃ , MnO, Fe ₂ O ₃ , and MoO _3. ..
Further, as Comparative Example 1, each layer was formed in the same manner as in Example 1 except that the oxide phase of the upper granular layer was _{composed of SiO 2.}

For these Examples 1-1 to 1-5 and Comparative Example 1, the roughness (Ra) and the inversion starting magnetic field (-Hn) with respect to the cap layer film thickness were measured. A comparison of them is shown graphically in FIGS. 3 and 4. In FIGS. 3 and 4, SiO ₂ is Comparative Example 1, ZnO is Example 1-1, WO ₃ is Example 1-2, MnO is Example 1-3, and Fe ₂ O ₃ is Example 1-4. MoO ₃ means Examples 1-5, respectively.

In both Examples 1-1 to 1-5 and Comparative Example 1, the lower granular layer is 67Co-23Pt-10SiO ₂ (mol%), and the cap layer is 60Co-10Cr-15Pt-5B. It was assumed to be (mol%).
Further, in Example 1-1, the upper granular layer was 62Co-21Pt-17ZNO (mol%) (ZnO = 30vol.%), And in Comparative Example 1, the upper granular layer was 67Co-22Pt-10SiO ₂ (mol%). (SiO ₂ = 30 vol.%). Upper granular layer, Example 1-2 In _{70Co-23Pt-7WO 3 (mol} %) (WO 3 = 30vol.%), 61Co-20Pt-19MnO (mol%) Example 1-3 (MnO = 30vol. %) example 1-4 In _{68Co-23Pt-10Fe 2 O 3} (mol%) (Fe 2 O 3 = 30vol.%), example 1-5 In _{62Co-21Pt-18MoO 3 (mol} %) (MoO ₃ = 30 vol.%).
The roughness (Ra) was measured by an atomic force microscope (AFM) manufactured by SII, and the reversal starting magnetic field (-Hn) was measured by a sample vibrating sample magnetometer (VSM) manufactured by Tamagawa Seisakusho.

From what is shown in FIG. 3, in Examples 1-1 to 1-5, even if the film thickness (tk) of the cap layer is thinner than that of Comparative Example 1 in which _{SiO 2 is used, a sufficient decrease in Ra is observed.} From this, it can be seen that the upper layer, the cap layer mainly composed of Co, and the Zn oxide are well wetted. Further, from FIG. 4, in Examples 1-1 to 1-5, d (−Hn) / dtc is positive in a range where the cap layer is thinner than that of Comparative Example 1 in which _{SiO 2 is used.} It can be seen that the SFD effect of the cap layer is obtained.

(Test Example 2)
As a reference example, 67Co-22Pt-10SiO ₂ (mol%) (SiO ₂ = 30 vol.%), Which is a Zn-free sputtering target, and 62Co-21Pt-17 ZnO (mol%) (ZnO =), which is a Zn-containing sputtering target. 30 vol.%) Was used to prepare a sample in which a single granular layer of 13 nm was formed on a film formed up to Ru in the same manner as in Test Example 1, and magnetic anisotropy Ku was measured.
The magnetic anisotropy (Ku) was measured with a magnetic torque meter (TRQ) manufactured by Tamagawa Seisakusho.

The value of Ku was 6.16 × 10 ⁶ erg / cc when the oxide of the granular layer was SiO ₂ , whereas it was 5.04 × 10 ⁶ erg / cc when ZnO was used. .. From this, it can be seen that Ku is lowered when a sputtering target containing Zn is used. Therefore, since a sputtering target having a composition high in Ku is often used for the lower granular layer, it can be said that it is desirable that the lower granular layer has a Zn-free layer.

(Test Example 3)
As an example 3-1~3-22, Co-Pt-ZnO, Co-Pt-SiO 2 -ZnO, Co-Pt-B 2 O 3 -ZnO, a sputtering target of Co-Pt-TiO ₂ -ZnO, A plurality of prototypes having different Zn contents were produced. The composition of each sputtering target is shown in Table 1 for reference.

A magnetic film was formed using each of these prototypes by the same method as in Test Example 1, and the roughness (Ra) and the inversion starting magnetic field (-Hn) with respect to the film thickness of the cap layer were measured. The above prototype was used for forming the upper granular layer of the magnetic film. The relationship between the Zn content and the film thickness of the cap layer in which Ra of the cap layer is less than 5 Å is shown in FIG. 5, and the relationship between the Zn content and the film thickness of the cap layer in which −Hn becomes positive is shown in FIG. Shown.
From FIG. 5, in particular, Examples 3-5 to 3-8, Examples 3-12 to 3-15, and Examples 3-19 to 3-22 in which the Zn content of the upper granular layer is 3 at% or more are cap layers. Since Ra is sufficiently reduced even if it is thin, it can be seen that the upper layer, which is mainly composed of Co, and the Zn oxide are further wetted. Further, from FIG. 6, in particular, Examples 3-5 to 3-8, Examples 3-12 to 3-15, and Examples 3-19 to 3-22 in which the Zn content of the upper granular layer is 3 at% or more are shown. Since the film thickness of the cap layer in which d (−Hn) / dtc becomes positive is considerably thin, it can be seen that the addition of Zn further improves SFD in the thin cap layer.

1 Recording layer 2 Granular layer 2a Boundary part 2b Remaining part 3 Cap layer 4a Metal phase 4b Oxide phase tg Overall thickness of granular layer tb Thickness of boundary part tc Thickness of cap layer

0003
[0009]
As a result of diligent studies, the inventor made the oxide of the metal and Co, etc. by including the oxide of a predetermined metal in the boundary portion of the granular layer located directly below the cap layer in the recording layer with the cap layer. Based on the good wettability with the cap layer containing a large amount of, the cap layer will be laminated on the non-magnetic part of the granular layer as well as on the magnetic part of the granular layer from the early stage of its growth. As a result, it was found that a uniform cap layer was formed on the granular layer. Further, since the oxide of a predetermined metal effectively separates the magnetic particles, when used as the metal oxide at the boundary portion of the granular layer, the required magnetic separability of the magnetic particles in the granular layer can be realized. it can.
[0010]
Based on this finding, the vertical magnetic recording medium of the present invention contains a metal oxide as a non-magnetic material, and the magnetic material is formed on a granular layer in which the magnetic material is dispersed in the non-magnetic material and the metal oxide. The oxide phase of the granular layer immediately below the cap layer at the boundary with the cap layer is Zn, W. , Mn, Fe and Mo, and the oxide phase of the boundary portion of the granular layer contains Zn.
[0011]
In the vertical magnetic recording medium of the present invention, the oxide phase at the boundary portion of the granular layer may further contain at least one of B and Si, and the granular layer may contain at least one of the above. The oxide phase at the boundary portion can further contain Ti.
[0012]
The perpendicular magnetic recording medium of the present invention preferably has a Zn-free layer in the rest of the granular layer except for the boundary portion.
In this case, the remaining portion of the granular layer contains an oxide of at least one element selected from the group consisting of Si, B and Ti as the oxide phase, and the total content of the oxide of the oxide phase in the remaining portion is contained. The amount is 20 vol. % ~ 50 vol. % Is even more preferable.

0003
[0009]
As a result of diligent studies, the inventor made the oxide of the metal and Co, etc. by including the oxide of a predetermined metal in the boundary portion of the granular layer located directly below the cap layer in the recording layer with the cap layer. Based on the good wettability with the cap layer containing a large amount of, the cap layer will be laminated on the non-magnetic part of the granular layer as well as on the magnetic part of the granular layer from the early stage of its growth. As a result, it was found that a uniform cap layer was formed on the granular layer. Further, since the oxide of a predetermined metal effectively separates the magnetic particles, when used as the metal oxide at the boundary portion of the granular layer, the required magnetic separability of the magnetic particles in the granular layer can be realized. it can.
[0010]
Based on this finding, the vertical magnetic recording medium of the present invention contains a metal oxide as a non-magnetic material, and the magnetic material is formed on a granular layer in which the magnetic material is dispersed in the non-magnetic material and the metal oxide. A cap layer that does not contain a cap layer is provided as a layer that constitutes at least a part of the recording layer, and the metal phase of the granular layer contains Co, and the metal phase of the granular layer immediately below the cap layer is the same as that of the cap layer. The oxide phase of the boundary portion contains at least one selected from the group consisting of Zn, W, Mn, Fe and Mo, and the oxide phase of the boundary portion of the granular layer contains Zn. Is.
[0011]
In the vertical magnetic recording medium of the present invention, the oxide phase at the boundary portion of the granular layer may further contain at least one of B and Si, and the granular layer may contain at least one of the above. The oxide phase at the boundary portion can further contain Ti.
[0012]
The perpendicular magnetic recording medium of the present invention preferably has a Zn-free layer in the rest of the granular layer except for the boundary portion.
In this case, the remaining portion of the granular layer contains an oxide of at least one element selected from the group consisting of Si, B and Ti as the oxide phase, and the total content of the oxide of the oxide phase in the remaining portion is contained. The amount is 20 vol. % ~ 50 vol. % Is even more preferable.

Claims (11)

At least a part of the recording layer is a granular layer containing a metal oxide as a non-magnetic material and the magnetic material dispersed in the non-magnetic material, and a cap layer formed on the granular layer and containing no metal oxide. The oxide phase of the granular layer immediately below the cap layer at the boundary with the cap layer is composed of Zn, W, Mn, Fe, and Mo. A vertical magnetic recording medium comprising at least one selected. The vertical magnetic recording medium according to claim 1, wherein the oxide phase at the boundary portion of the granular layer contains Zn. The perpendicular magnetic recording medium according to claim 1 or 2, wherein the oxide phase at the boundary portion of the granular layer further contains at least one of B and Si. The perpendicular magnetic recording medium according to any one of claims 1 to 3, wherein the oxide phase at the boundary portion of the granular layer further contains Ti. The perpendicular magnetic recording medium according to any one of claims 1 to 4, wherein the remainder of the granular layer except the boundary portion has a Zn-free layer. The balance of the granular layer contains an oxide of at least one element selected from the group consisting of Si, B and Ti as the oxide phase, and the total content of oxides of the oxide phase in the balance is 20 vol. .. % ~ 50 vol. The perpendicular magnetic recording medium according to claim 5, which is%. The perpendicular magnetic recording medium according to any one of claims 1 to 6, wherein the oxide phase at the boundary portion of the granular layer contains Zn, and the Zn content of the oxide phase is 3 at% or more. The perpendicular magnetic recording medium according to any one of claims 1 to 7, wherein the ratio of the thickness of the boundary portion to the thickness of the entire granular layer in the stacking direction of the recording layer is 3% to 50%. The invention according to any one of claims 1 to 8, wherein the entire granular layer including the boundary portion contains at least one metal selected from the group consisting of Co, Pt, Ru and Cr as the metal phase. Perpendicular magnetic recording medium. The perpendicular magnetic recording medium according to any one of claims 1 to 9, wherein the cap layer contains at least one metal selected from the group consisting of Co, Cr, Pt and B. The perpendicular magnetic recording medium according to any one of claims 1 to 10, wherein the thickness of the cap layer is 1 nm to 3 nm in the stacking direction of the recording layer.

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